Questions about standards (measuring rods) for micrometers

[astjp2]

I give a lot of credit to you machinists who have customers. I get enough of that at work.

In my shop, I am too selfish about my creative freedom to allow in others who might alter the path that I want to take. Again, I get more than enough of that at work.

Having said that, I retire in a little over 11 years, and I might change my tune when I need customers’ money.

I work on airplanes and for the most part I have good customers but just a couple are bad enough for me to want to get out of business... I used to enjoy it, now it has become a chore that pays the bills. The ones that are the worst are when you are charging less than most people in my area, I have to travel to them and no matter what, its too much and they nit pick everything you do. Tim

 

[Buffalo21]

My great-uncle, always said, “you machine to the tolerance the customer is willing to pay for, the tighter the tolerance, the more it cost”

 

[MrWhoopee]

The ones that are the worst are when you are charging less than most people in my area, I have to travel to them and no matter what, its too much and they nit pick everything you do. Tim

I have fired a few of these. It's the old 80/20 rule, they are 80% of your grief and 20% (or less) of your income.

 

[stuarth44]

Regarding measuring rods for outside micrometers, my questions are:

(1) to what degree do you trust import measuring rods?,
2) do you zero your micrometer before using it?, and
(3) should I be concerned about buying used measuring rods?

For my imperial mikes, I have Shars standards and Shars gage blocks.

For my metric mikes, I bought used Starrett and Mitutoyo standards.

As far as what tolerance I am shooting for, it doesn’t actually matter, BUT I do take my hobby seriously and I shoot for .001” or better. I fail more often than I succeed. I am striving to be able to work to .0003” one day; like I said, it will probably never have any practical application because most of what I do is just an exercise.

I make no effort for temperature control, but I do make an effort to clean the surfaces of oil before I take measurements. That should give you an idea of what precision I am aiming for. For myself, I consider anything much over a thou out to be a failure (or should I say a learning experience?).

bit late here, all my digi verniers are out, according to my Starrett standard and by quite a way too, they are not well known makes but hell!!

 

[erikmannie]

bit late here, all my digi verniers are out, according to my Starrett standard and by quite a way too, they are not well known makes but hell!!

Well, that’s not good! +1 for dial type (analog) calipers.

 

[MrWhoopee]

bit late here, all my digi verniers are out, according to my Starrett standard and by quite a way too, they are not well known makes but hell!!

I'm a little confused. Are they digital or vernier, how many and how far out?

 

[pontiac428]

Something to ponder: you can never calibrate a micrometer. A micrometer is linear, or y=mx+b in slope-intercept form. There ate two terms, m (slope) and b (intercept). You can adjust the intercept; that is called zeroing, and it's what you do with your standard. But you cannot change the x/y relationship, that is ground into the threads of the mic barrel. All you can do is VERIFY calibration with a check standard. If your mic measures 1.010" over it's range on a 1.000" standard, and 2.040 on a 2" standard, you can't adjust that out, so the caliper would be disposed of. You can adjust the zero for 1.000 and 2.030, but you can't make that second reading change in any way.

Between micrometers, technique, temperature, and anything else we can think of to control, there will always be issues that skew your measurement off of the true value. Hence measurement error, error budget factors, and compounding errors that all go into effect when deriving precision and accuracy. These are the reasons I don't work to 10ths!

 

[JRaut]

I check my mics every couple seasons or so.

My shop is in my basement. Climate control is better than an unheated garage/shed, but it ain't 72* year-round. It gets up to the 80s or so in the summer and down to the 50s or so in the winter.

Sometimes I have to give one or two a little tweak, but never more than a couple tenths' worth.

 

[Winegrower]

I work on airplanes and for the most part I have good customers but just a couple are bad enough for me to want to get out of business... I used to enjoy it, now it has become a chore that pays the bills. The ones that are the worst are when you are charging less than most people in my area, I have to travel to them and no matter what, its too much and they nit pick everything you do. Tim

I have thought for a long time that the biggest problem in aviation are the pilots.

 

[stuarth44]

I'm a little confused. Are they digital or vernier, how many and how far out?

digital verniers, I'd have to check how far out